Koestner A
Biol Res Pregnancy Perinatol. 1983;4(1):17-21.
Known and unknown host factors determine the individual susceptibility to carcinogenic agents. Such factors may interact with either the phase of transformation (initiation) or with the phase of proliferation (promotion). Some of these factors have been recognized as potential determinants of the degree of susceptibility or resistance to cancer. Transformation may be impeded by a low rate of absorption of carcinogenic agents (barrier effect), by the availability of deactivating enzymes operative at several steps of the metabolism of carcinogenic agents, and by a high repair capability of DNA damage. Proliferation of transformed cells may be impeded or prevented by immune defense mechanisms and by maturation factors such as nerve growth factor (NGF), glia maturation factor, fibroblast growth factor, and others. NGF has already been shown to be capable of maturing anaplastic glioma cells (clone F98) and reducing their rate of growth. Rats treated with NGF following implantation of anaplastic glioma cells had a significantly decreased tumor growth rate and increased survival time. NGF administration to pregnant rats preceding exposure to ethylnitrosourea (ENU) (50 mg/kg, 21st day of gestation) or to offspring transplacentally exposed to ENU resulted in reduction of neurinoma development. The importance of NGF as a suppressing agent of neoplastic proliferation and as a prospective tumor therapeutic needs further exploration.
已知和未知的宿主因素决定了个体对致癌剂的易感性。这些因素可能与转化阶段（启动）或增殖阶段（促进）相互作用。其中一些因素已被认为是癌症易感性或抗性程度的潜在决定因素。致癌剂的低吸收率（屏障效应）、在致癌剂代谢的几个步骤中起作用的失活酶的可用性以及DNA损伤的高修复能力可能会阻碍转化。免疫防御机制以及神经生长因子（NGF）、神经胶质成熟因子、成纤维细胞生长因子等成熟因子可能会阻碍或阻止转化细胞的增殖。已经证明NGF能够使间变性胶质瘤细胞（克隆F98）成熟并降低其生长速度。间变性胶质瘤细胞植入后用NGF治疗的大鼠肿瘤生长速度显著降低，存活时间延长。在怀孕大鼠接触乙基亚硝基脲（ENU）（50 mg/kg，妊娠第21天）之前或对经胎盘接触ENU的后代给予NGF，可减少神经鞘瘤的发生。NGF作为肿瘤增殖抑制剂和潜在肿瘤治疗剂的重要性需要进一步探索。
